Concentrated single phase aqueous solutions of tetrahydroiso-α-acids and methods of preparing the same

Abstract

A concentrated single phase aqueous alkaline solution of tetrahydroiso-α-acids having greater than 10% to about 45% w/w tetrahydroiso-α-acids is disclosed. A method of hydrogenating and formulating a starting solution of iso-α-acids to obtain such concentrated solutions of tetrahydroiso-α-acids is also disclosed.

We claim: 
     
       1. A method of preparing a single phase aqueous alkaline solution consisting essentially of tetrahydroiso-α-acids, comprising the steps of: dissolving an aqueous alkaline solution of iso-α-acids of the formula ##STR3## in a lower alkanol solvent, wherein the alkaline solution is about 10% to about 45% w/w iso-α-acids;   reducing the iso-α-acids in the presence of about 1-2000 psig of hydrogen and a palladium on carbon catalyst at about 20°-100° C. to form tetrahydroiso-α-acids;   filtering the solution to remove the catalyst; and   removing the alkanol solvent to form the single phase aqueous alkaline solution consisting essentially of greater than about 10% to about 45% w/w tetrahydroiso-α-acids of the formula ##STR4##   
     
     
       2. The method of claim 1, wherein the temperature is about 20°-50° C. 
     
     
       3. The method of claim 1, wherein the temperature is about 40°-45° C. 
     
     
       4. The method of claim 1, wherein the hydrogen pressure is about 1-50 psig. 
     
     
       5. The method of claim 1, wherein the hydrogen pressure is about 20 psig. 
     
     
       6. The method of claim 1, wherein the lower alkanol is ethanol. 
     
     
       7. The method of claim 1, wherein the alkanol solvent is removed by distillation. 
     
     
       8. The method of claim 1, wherein the alkanol solvent is removed by evaporation. 
     
     
       9. The method of claim 1, wherein the single phase aqueous alkaline solution is about 15%-25% w/w tetrahydroiso-α-acids. 
     
     
       10. The method of claim 1, wherein the single phase aqueous alkaline solution is about 25%-35% w/w tetrahydroiso-α-acids. 
     
     
       11. The method of claim 1, wherein the single phase aqueous alkaline solution is about 35%-45% w/w tetrahydroiso-α-acids. 
     
     
       12. The method of claim 1, wherein the aqueous alkaline solution of iso-α-acids has a pH of about 6-10. 
     
     
       13. The method of claim 12, wherein the aqueous alkaline solution of iso-α-acids has a pH of about 8-9. 
     
     
       14. The method of claim 12, wherein the aqueous alkaline solution of tetrahydroiso-α-acids has a pH of about 6-10. 
     
     
       15. The method of claim 14, wherein the aqueous alkaline solution of tetrahydroiso-α-acids has a pH of about 8-9. 
     
     
       16. The method of claim 1, wherein the aqueous alkaline solution of iso-α-acids is a potassium hydroxide solution. 
     
     
       17. The method of claim 1, wherein the aqueous alkaline solution of tetrahydroiso-α-acids is a potassium hydroxide solution. 
     
     
       18. A single-phase aqueous alkaline solution consisting essentially of greater than 10% to about 45% w/w tetrahydrosio-α-acids of the formula ##STR5## 
     
     
       19. The solution of claim 18, wherein the solution has a pH of about 6-10. 
     
     
       20. The solution of claim 19, wherein the solution has a pH of about 8-9. 
     
     
       21. The solution of claim 18, wherein the tetrahydroiso-α-acids are about 15%-25% w/w. 
     
     
       22. The solution of claim 18, wherein the tetrahydroiso-α-acids are about 25%-35% w/w. 
     
     
       23. The solution of claim 18, wherein the tetrahydroiso-α-acids are about 35%-45% w/w. 
     
     
       24. The solution of claim 18, wherein the solution is an aqueous potassium hydroxide solution. 
     
     
       25. A single-phase aqueous alkaline solution consisting essentially of tetrahydroiso-α-acids prepared by the method of claim 1.